In general, almost every vehicle employs a steering system that assists using a separate power as a device for guaranteeing a steering stability of the vehicle. Conventionally, the auxiliary steering device uses hydraulic pressure, but an EPS (Electronic Power Steering) system adapted to transmit a rotation output of an electric motor to a steering shaft via a speed reduction mechanism has been increasingly employed these days from a viewpoint of a reduction in engine load, a reduction in weight, an enhanced steering stability and a quick restoring force.
The EPS system is such that an ECU (Electronic Control Unit) drives a motor in response to steering conditions detected by a speed sensor, a torque angle sensor and a torque sensor to enhance a steering stability and provide a quick restoring force, whereby a driver can safely steer a vehicle.
The torque sensor in the EPS is configured such that a magnet is disposed along a periphery of a rotor, and a stator formed with a lug piece corresponding to a polarity of the magnet is disposed at a periphery thereof, where magnetic charge is outputted in response to a difference of mutual rotations to detect torques of input shaft and output shaft, and the torques are transmitted to an ECU. In addition, a torque angle sensor detects a torque applied to a steering shaft, outputs an electric signal proportional to the detected torque, and outputs an electric signal proportional to a rotation angle of the steering shaft.
In this configuration, the stator is realized by an integral structure having a plurality of protruding pieces, which is in turn realized by a method of processing in an integral structure from a single sheet at the time of manufacturing, resulting in a disadvantageous problem of generating a loss of cost due to increased waste of raw materials.